When an Imperial player has a new deployment point become active during the Campaign Status Phase, does the original deployment point remain active or is it no longer usable? I think some missions state rules about this, but some do not specify. So I'm thinking I have the choice of deployment points in the mission doesn't indicate the old point is closed.

From Rules Ref:

• When the location for a figure’s deployment is not specified, it

is deployed as close as possible to any active deployment point

shown in the mission’s diagram, chosen by the Imperial player.

This includes the space containing the deployment point.

-- Green deployment points are active at the start of each

mission. Red, blue, and yellow deployment points are not

active until specified by the mission’s rules, even if another

rule allows a one-time deployment to any of those points.

When an Imperial player has a new deployment point become active during the Campaign Status Phase, does the original deployment point remain active or is it no longer usable? I think some missions state rules about this, but some do not specify. So I'm thinking I have the choice of deployment points in the mission doesn't indicate the old point is closed.

Your thinking is correct. If the mission rules do not specify that the original deployment points are no longer active, then they are still active.